Stockholders' Equity (Deficit) - December 2024 Securities Purchase Agreement (Details) - USD ($) $ / shares in Units, $ in Millions	Aug. 13, 2025	Jul. 01, 2025	Mar. 21, 2025	Feb. 11, 2025	Dec. 17, 2024	Mar. 04, 2024	Jan. 12, 2024	Sep. 30, 2025	Sep. 25, 2025	Mar. 20, 2025	Jan. 31, 2025	Sep. 15, 2024
Class of Warrant or Right [Line Items]
Exercise price (in dollars per share)				$ 4.32	$ 6.82		$ 13.44
Warrants and rights outstanding, term (in years)		5 years		5 years	5 years
Aggregate cost	$ 2.7		$ 2.1		$ 5.0	$ 4.0	$ 4.0
Estimated issuance costs					0.5
Proceeds from Issuance of Warrants					$ 4.4
Pre-Funded Warrants
Class of Warrant or Right [Line Items]
Number of warrants exercised on net basis (in shares)		2,156,880		973,886	40,000
Class of warrant or right, gross proceeds and issued warrants percentage (as percent)					7.00%
Common Warrant
Class of Warrant or Right [Line Items]
Number of warrants exercised on net basis (in shares)		2,836,880		1,273,886
Placement Agent Warrants
Class of Warrant or Right [Line Items]
Number of warrants exercised on net basis (in shares)				63,694
Warrants and rights outstanding, term (in years)					5 years
Class of warrant or right, gross proceeds and issued warrants percentage (as percent)												7.00%
Fair value of warrants					$ 0.3							$ 0.1
Common Class A
Class of Warrant or Right [Line Items]
Number of shares sold (in shares)		680,000	1,071,429	300,000	230,000	94,286	64,286
Number of warrants exercised on net basis (in shares)		1,157,143							675,000			714,286
Exercise price (in dollars per share)			$ 1.93		$ 6.08			$ 8,050		$ 3.80
Warrants and rights outstanding, term (in years)								5 years
Common Class A \| December 2024 Purchase Agreement
Class of Warrant or Right [Line Items]
Shares issued (in dollars per share)					$ 6.20
Number of warrants exercised on net basis (in shares)					367,000						203,000
Common Class A \| Pre-Funded Warrants
Class of Warrant or Right [Line Items]
Number of warrants exercised on net basis (in shares)					570,000
Exercise price (in dollars per share)		$ 0.00001		$ 0.00001	$ 0.00001
Common Class A \| Common Warrant
Class of Warrant or Right [Line Items]
Number of warrants exercised on net basis (in shares)					800,000
Exercise price (in dollars per share)		$ 1.41		$ 3.80
Common Class A \| Placement Agent Warrants
Class of Warrant or Right [Line Items]
Number of warrants exercised on net basis (in shares)												35,715
Exercise price (in dollars per share)												$ 8.86

Momentus Inc. 10-Q